1. Technical Field
The present invention relates to a cellular radio communications device, and related method of operation aid, in particular, to a mobile phone and related method of operation.
2. Prior Art
Mobile phone comprises a master clock circuit for generating a relatively high frequency clock signal which forms part of the timebase circuitry within the mobile phone. The timebase generated within the mobile phone is intended to be synchronized with a timebase of a base station with which the mobile phone communicates in accordance with a particular communication system such as, for example, the Global System for Mobile Communication (GSM).
A plurality of mobile communication systems available have been developed which require different master clocks and timebases for their operation.
A mobile phone offering access to two or more such systems would therefore be advantageous since the same mobile phone handset could then be used with a selected one of the different communication systems supported. This choice of system for the same mobile phone would therefore lead to a greater geographical coverage for one and the same mobile phone since different communication systems commonly exhibit different geographical boundaries. This geographical limit commonly occurs at international boundaries and also occurs as a consequence of the time taken to achieve full coverage of a network technology. Such a dual mode mobile phone would therefore be particularly attractive to users who travel overseas and also to the early users of new technology communications systems.
For such dual mode mobile phones and, for example, for those employing the Universal Mobile Telecommunications System (UMTS) and GSM, it has been identified that there is a requirement to measure the time period between defined points in the timebase of, for example, a UMTS serving cell and each GSM neighbouring cell.
While this application is primarily aimed at dual mode UMTS GSM usage, the principles described can be used on any systems using a well defined timebase. The principles can also be used without significant modification in cellular equipment operating on more than two systems.
It has been identified that such a timing offset is required in order to allow for full interoperability between the different communication systems and thus allow for the execution of full dual-mode operations within the mobile phone handset.
The offset needs to be known to allow specified times on one system and to be translated into the timebase of the other system (and vice versa). Without knowledge of the offset such translation is not possible and coordination of operation of the two systems would bot prove possible.